With the development of industrial production, an accuracy requirement of a flowmeter is high. A working principle of a mass flowmeter is based on the flow rate of a fluid which affects a temperature of a sensing element, thereby changing a resistance of the sensing element, and by measuring the change in the resistance of the sensing element, the flow rate can be measured.
According to the law of resistance, the resistance formula of the sensing element is R=ρL/S, where, ρ is the resistivity of the sensing element, L is the length of the sensing element, S is the cross sectional area of the sensing element. The resistivity ρ is associated with the temperature of the sensing element. When the length of the sensing element is unchanged, the smaller the cross sectional area, the greater will be the resistance of the sensing element as affected by the temperature. Therefore, the smaller a diameter of the sensing element, the higher will be the sensitivity of the sensing element anemometer.
The conventional sensing element is a metal wire. However, when a diameter of the metal wire made of metal or metal alloy is in micrometer size or less, the metal wire is easily broken. Therefore, the sensitivity of the conventional mass flowmeter is bad, and a life of the sensing element is short.